This invention pertains to valves and especially to gate valves suitable for high-pressure cryogenic service. The invention is specifically directed to a gate valve having a single seat and disc that are urged into sealing engagement with one another by the action of the engagement of two sets of mating cam surfaces as the disc hanger or gate is lowered into position.
Gate valves have been used extensively for quite sometime, primarily in the petroleum industry as control valves for gas and oil pipelines. In addition, valves of various types have utilized a single disc and seat in various applications, typically water hydrants, as shown in U.S. Pat. Nos. 373,522, 224,061 and 653,600. These water hydrants typically utilize a single seat which travels vertically down a threaded shaft to engage a cam means to urge the valve disc against the valve seat. In this type of valve, the cam means is a single device positioned in the fluid medium flow passage and necessarily obstructs fluid flow therethrough. In addition, those prior art devices utilizing a universal joint means of attaching the valve element disc to the carriage or hanger are not of the in-line, flow through type. Consequently, they created turbulence within the valve due to obstructions within and the fluid flow being diverted therearound.
It is therefore an object of the present invention to provide gate valve having an in-line flow passage therethrough, having a single disc and seat that has limited universal movement with respect to its carrying body to aid in seating against the valve seat, and having a valve mechanism that is removed from the valve flow passage when in open position to reduce fluid flow turbulence within the valve.